The present invention relates to a hydraulic cylinder that has two oppositely acting pistons with differential areas and which can be used for locking two parts that are slidable relative to each other.
Backhoes and excavators that mount onto mobile machines are generally provided with lateral or horizontal rails mounted onto the support machine with a slide frame that slides along these rails from side to side.
A typical backhoe structure that is mounted for side shifting of the type disclosed herein but without the type of locks utilized is illustrated in my own U.S. Pat. No. 4,921,392, which is of general interest for showing the overall mounting arrangement.
It is necessary to have the slide frame locked tightly to the rails so that the slide frame will not tilt or shift during use. Hydraulic lock cylinders have been used for clamping slide frames onto rails, such as the devices shown in U.S. Pat. No. RE 26,439 issued to E. B. Long. There, direct acting hydraulic cylinders will provide compression clamping against the rails.
The prior art also shows wedge-type locking devices which will force the slide frame in one direction to wedge it into locking engagement with support rails. Such a device is shown in U.S. Pat. No. 4,741,663. U.S. Pat. No. 3,405,823 shows a direct acting wedge that can be hydraulically locked into position. In U.S. Pat. No. 3,891,065, hydraulic actuators are positioned between the guide and are expanded to move wedges relative to the rails for locking.
The present invention provides for rapid locking and positive positioning with a relatively simple lock cylinder that is easily mounted and operated.